Lysophospholipids, LPA and S1P, stimulate endothelial cell proliferation and migration, suggesting that these lipids may act as angiogenic regulators. In this proposal, we aim to determine the mechanisms induced by LPA and S1P in regulating endothelial cell function. We will determine the abilities of LPA and S1P to modulate the capacity of endothelial cells to produce and respond to VEGF, a major angiogenic factor. We will determine the effects of LPA and S1P on 1.) the expression of VEGF in endothelial cells by immunoprecipitation (IP), ELISA and Northern blot analysis; 2.) the expression levels of the VEGF receptors on endothelial cells by IP and quantitative RT-PCR; 3.) the phosphorylation of VEGF receptors by IP-Western. Furthermore, we will determine the mechanisms activated by LPA and S1 P induced- endothelial cell proliferation and migration. We will determine the effects of LPA and S1P on adhesion of endothelial cell. The expression patterns of adhesion molecules on endothelial cell surface will be assessed by FACS and Northern blot analysis. The effects of lysophospholipids on endothelial cell proliferation will be assessed by using reporter gene assays. Signal pathways induced in endothelial cell migration and proliferation triggered by lysophospholipids will be assessed by using specific inhibitors.